The Order of Importance
Some might quibble with the order of the laws. For example, one manager told me: “In our shop, performance is of highest importance. We have service level agreements that we must meet in order to meet our customer’s needs. Performance is more important than backup and recovery.”
Actually, performance is certainly an urgent concern, but recoverability remains the most important. To determine what’s really important, consider an anecdote:
You’re a DBA supporting IT systems for a provider of medical and surgical services. Your systems are used daily by doctors, nurses, and technicians to provide services to patients. In some cases, these services (e.g., diagnosis) may involve life-or-death decisions. Your supervisor asks you to give a presentation to upper management (including the CIO, vice president of IT, and major stockholders or owners) of new enhancements your department will make. Your presentation begins as follows:
“Ladies and gentlemen, the DBA team will be implementing some high-performance features in the near future. We have two implementation plans and we’d like your assistance in choosing between the two.
“Plan A will involve performance changes that will result in up to 95 percent of our online transactions finishing in their required service levels.” You hear some grumbling from the audience, as they realize this means 5 percent of the online transactions will perform poorly. You continue.
“Plan B will involve performance changes resulting in 100 percent of our online transactions finishing in their required service levels.” You hear sighs of relief from your audience, as they are clearly more comfortable with this plan.
“However,” you continue, “if we have a major hardware outage, there’s a good possibility that up to 5 percent of our data will be missing or invalid.”
Your audience now sits in stunned silence. They realize there could be a power outage or other disaster that affects the IT systems. Should this occur, when the systems come back up, every user will know there’s a 5 percent chance that test results are missing, diagnoses are incorrect, or that some patient’s records will have completely disappeared.